I am wondering how you make bonsai plants grow small... Something to do with cutting roots and training branches?

I have an interest in them and I am well aware it takes years and years but thats ok...

So for now Im just trying to figure a few things out...

Silk floss tree, monkey pod tree and pencil palm are a few I thought to look nice so far but I need to know how the plants grow small... I dont think they do it by themselves, so how can I find out step by step how to make a little plant small and turn it into a bonsai?

It will take years to grow anything from seed and even then it will be more of a sapling than a bonsai. Most people start off with a prebonsai or young field grown tree that they prune down and place in a pot.

Short answer is that they stay small by growing in a confined pot along with branch and root pruning.